This invention relates to a seat cushion support for an upholstered seat, and especially to a molded one-piece form-retaining resilient plastic support member for an upholstered motor vehicle seat.
A motor vehicle seat cushion assembly, that term here being used to refer to a seat bottom as distinguished from a seat back assembly, typically comprises a seat frame having a plurality of springs stretched on a metal frame. A cushion or pad is placed over the springs and an upholstery cover is applied, e.g. by stitching, over the entire structure. Typically, the springs are of the coiled or serpentine type, or both. It is well known to those skilled in the motor vehicle seating art that such seat assemblies, i.e., those having a conventional open seat frame with a plurality of conventional springs secured thereto, have numerous inherent disadvantages. One such inherent disadvantage is the high cost of conventional steel springs having suitable elastic characteristics. In addition, the assembly of the frame, including the numerous springs which must be attached to the frame, is a labor intensive and expensive operation. Also, a thick cushion or pad is required to adequately distribute and transfer the seat occupant's weight and to protect the seat occupant from discomfort due to contact with the springs or frame. In addition, upholstery may be torn or otherwise damaged during manufacture and use of such seats by springs which become detached at one end from the frame. Another significant disadvantage is the weight of such frame and spring assemblies. This is of particular concern in the manufacture of motor vehicles, where reduced weight contributes directly to improved fuel economy.
Various structures have been proposed, and occasionally used, as alternatives to conventional open seat frames having a plurality of conventional springs. Thus, for example, U.S. Pat. No. 4,502,731 to Snider discloses a one-piece seat frame comprising a thin-walled, hollow, molded body of plastic or other suitable, relatively rigid yet resilient material. The molded body of Snider has a pair of side walls, a rear wall, a front wall, an open bottom and a positively bowed top wall. A plurality of parallel curvilinear slots are Provided through the top wall to form a plurality of parallel curvilinear segments which act as cantilever-action spring elements. It is taught therein that in response to a typical load created by a seat occupant, the spring elements are deflected downward in a cantilever manner. Similar teaching is provided, for example, in U.S. Pat. No. 3,399,883 to McKey, wherein is disclosed a seat frame structure consisting essentially of a single sheet of resilient material which functions as a flexible or resilient support means for a seat assembly. Two rows of parallel tapered slots permit the mid-portion of a sheet to assume the contour of the load created by the seat occupant. A similar seat frame structure is disclosed in U.S. Pat. No. 2,804,129 to Propst, wherein a single seat of resilient material is provided with parallel untapered slots around its periphery. Each such slot terminates in a circular recess.
All such prior structures comprising formed resilient support assemblies, however, fail to adequately meet the unique and stringent requirements of motor vehicle seating structures. Most notably, for example, a suitable seat support structure for a motor vehicle must provide excellent vibration isolation for the seat occupant. In addition, it must have load/deflection characteristics suitable to comfortably accommodate the typical ingress and egress path to the side of such seating used by motor vehicle occupants. In addition, motor vehicle seating must provide a high degree of comfort for the seat occupant in view of the possibly long periods of seat occupation and transmission to the seat occupant of at least a measure of vibration due to road roughness. Another significant feature sought in motor vehicles seating is that the seat support characteristics should be tunable, that is, adjustable from one vehicle to another or from one vehicle line to another with little or no change in the design of the structure and also, preferably, adjustable by the seat occupant.
It is an object of the present invention to provide an upholstered seat cushion support, especially a one-piece seat cushion support for motor vehicle seating, which is easily tunable in its load bearing characteristics with little or no change of design. Other objects and advantages of the present invention will be understood from the following disclosure.